Caption: Coloured scanning electron micrograph (SEM) of Common house mosquito ovipositor (Culex spp.). A female releases her eggs from a structures at the tip of her abdomen called an ovipositor. Culex species lay their eggs in the form of egg rafts that float in still or stagnant water. In the United States, West Nile virus is transmitted primarily by Culex pipiens mosquitoes. Culex spp. become infected by biting certain birds carrying the West Nile virus and in turn transmits the virus to humans where it can cause encephalitis and meningitis. Culex spp. are also disease vectors of western equine and Saint Louis encephalitis. In addition, Culex spp. are carriers of viral encephalitis and filariasis. Magnification: x20 when shortest axis printed at 25 millimetres.